His work on these and other problems won him recognition and a position as an associate professor at Harvard in 1990.[2] In 1993, he was made a full, tenured professor at the age of 26. This made him the youngest full professor in the history of Harvard, surpassing previous then-youngest professors Alan Dershowitz, Jeffrey Sachs,[6]William H. Press, and Lawrence Summers (who were each made full professors at age 28).[7]